diff --git a/ChangeLog b/ChangeLog
index 2f8109c840..c787135999 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sun Jan  1 15:28:46 2006  Tanaka Akira  <akr@m17n.org>
+
+	* missing.h (isnan): avoid macro expantion
+	  "extern int isinf(double);" to
+	  "extern int ((sizeof(double)==sizeof(float))?_Isinff(double):_Isinf(double));" on
+	  HP-UX.
+
 Sun Jan  1 14:42:54 2006  Hirokazu Yamamoto  <ocean@m2.ccsnet.ne.jp>
 
 	* win32/win32.c (rb_w32_seekdir): should not segfault even if passed
diff --git a/missing.h b/missing.h
index 5b4dcc2747..1b9ca2e20b 100644
--- a/missing.h
+++ b/missing.h
@@ -62,11 +62,13 @@ extern double erf(double);
 extern double erfc(double);
 #endif
 
-#ifndef HAVE_ISINF
-# if defined(HAVE_FINITE) && defined(HAVE_ISNAN)
-# define isinf(x) (!finite(x) && !isnan(x))
-# else
+#ifndef isinf
+# ifndef HAVE_ISINF
+#  if defined(HAVE_FINITE) && defined(HAVE_ISNAN)
+#  define isinf(x) (!finite(x) && !isnan(x))
+#  else
 extern int isinf(double);
+#  endif
 # endif
 #endif